The present invention relates to an ultrasonic diagnostic apparatus for transmitting ultrasonic signals from ultrasonic transducers toward a subject to be examined, and receiving reflected waves of the ultrasonic signals for display, and more particularly to an ultrasonic diagnostic apparatus of small size and low power consumption.
Conventionally, an ultrasonic diagnosis for imaging the interior of a subject by applying ultrasound to a region to be examined in the subject with an abutting ultrasonic probe, and producing an image of echo signals of reflected waves of the applied ultrasound is commonly used. Since ultrasound is harmless to a living body, the ultrasonic diagnostic apparatus is especially useful for medical applications and is used for detection of foreign material in the living body, determination of lesion degree, observation of a tumor or a fetus, and the like.
In recent years, size and weight reduction of an ultrasonic diagnostic apparatus is desired. An ultrasonic diagnostic apparatus of small size and light weight overall will desirably provide an ultrasonic diagnostic apparatus that can be easily carried. A problem in reducing the size and weight of the ultrasonic diagnostic apparatus is especially in a power source section. Since the ultrasonic diagnostic apparatus requires provision of a transmitter power source for ultrasonic transducers, and in addition, a bias power source for an analog switch, attempts have been made to reduce the size of these power sources.
A conventional method for reducing the size of the power source involves generating transmitter power source from a bias power source for an analog switch (for example, see Patent Document 1).
[Patent Document 1]
Japanese Patent Application Laid Open No. 2002-306475.
In the conventional ultrasonic diagnostic apparatus, however, although size reduction of the apparatus is achieved by combining the transmitter power source and bias power source, a problem of a large power loss arises.
Specifically, since it is necessary for the voltage of the bias power source to be higher than that of the transmitter power source, the conventional ultrasonic diagnostic apparatus is configured to obtain the transmitter power source from the bias power source via a voltage drop circuit (direct current stabilizing power source circuit). In such a configuration, if the voltage supplied from the transmitter power source to the ultrasonic transducers is low, the voltage difference between the bias power source and transmitter power source becomes large, resulting in the large power loss.
Such a power loss leads to a problem of shorter usable time and larger heat generation in a portable ultrasonic diagnostic apparatus in which the ultrasonic transducers are driven by a battery.